Hi looking for advice before I go nuts.
Got a stern powr 1000 series pain in the @&'! Outdrive leg powered by diesel inboard mermaid turbo four 140hp.
It's always been hard to steer hydraulically even at 12knots so I looked into what could be issues like air in system or pump and ram issues.
Firstly I replace all oil and bled the system of air and also left it to settle over night and checked for micro bubbles, all fine. Take boat for test still stiff.
Disconnected ram from leg and I can move leg by manually pushing it side to side.
Operate the ram not connected to leg but with hoses connected all ok, check pin in leg to secure ram, all good moving freely.

So get a new sea star pump from hypro marine and fit with new hoses and fittings. The ram been inspected and seems ok with no leaks or obvious damage but I can't source a new one as it's an obsolete hynautic ram and even the right people say they haven't got anything to update this ram due to securing mount onto the stern powr mounting bracket, lancing marine could source one but at £800 for the small ram.
Anyway now with the new pump and hoses all back on and all air bled correctly on testing the steering seems even stiffer so any ideas what I'm over looking or doing wrong.

Yes I done that and I can move the leg by hand. The leg got serviced in February as we were unsure when it was last done £3000 it cost as most new parts from America. But we noticed at the weekend one of the 4 leg trim hoses has blown so cant trim the leg but it is in the fully down position. Would this add to the issue of steering.

If it has always been heavy, how do you know whether it had the right pump on to start with? If the wrong pump has been fitted before you got it, you might be repeating the error? Is there no information on what pump it should have?

No peter there is no separate accumulator and it is a passive system.
After these suggestions I will do some net research to see if I had the right helm from the beginning, i need to find a ex sbs service man who knows about these as I can never get any answer from stern powr in the states.
I will also give lancing marine a call as they are agents.

With the ram disconnected and system powered up, the ram did not change position from center did it? That would show a leak in the helm controls.

When moving the steering back and forth does the ram follow at approximately the correct amount of travel? This would show the helm is flowing juice correctly although maybe not at the right pressure.

Air in the system will froth the fluid and typically makes noise.

At this point you just need to run every test you can create and then put all the pieces together to make an assement. Getting the right part numbers and cross checking them would be a good idea, as suggested for the pump but also the helm and ram. For instance if the ram is too big it would feel sluggish with little assistance. Too small of a ram would slam the outdrive back and forth in a hurry.